body{margin:0;min-width:320px}:root{--primary: #4f46e5;--primary-hover: #4338ca;--bg: #f8fafc;--card-bg: #ffffff;--text: #1e293b;--text-light: #64748b;--border: #e2e8f0;--error: #ef4444;--success: #22c55e;--radius: 12px}*{box-sizing:border-box;margin:0;padding:0}body{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;background:var(--bg);color:var(--text);line-height:1.6}.app{min-height:100vh;display:flex;flex-direction:column;max-width:700px;margin:0 auto;padding:16px;transition:max-width .3s ease}.app.app-wide{max-width:1120px}header{text-align:center;padding:16px 0;border-bottom:1px solid var(--border);margin-bottom:24px}header h1{font-size:1.5rem;color:var(--primary)}.topic-badge{display:inline-block;margin-top:8px;padding:4px 12px;background:var(--primary);color:#fff;border-radius:20px;font-size:.85rem}main{flex:1}.step-card{background:var(--card-bg);border-radius:var(--radius);padding:24px;box-shadow:0 1px 3px #0000001a}.step-card h2{margin-bottom:16px;font-size:1.3rem}form{display:flex;flex-direction:column;gap:16px}label{display:flex;flex-direction:column;gap:6px;font-weight:500;font-size:.95rem}input[type=text],select{padding:12px;border:2px solid var(--border);border-radius:8px;font-size:1rem;transition:border-color .2s}input[type=text]:focus,select:focus{outline:none;border-color:var(--primary)}button{padding:12px 24px;background:var(--primary);color:#fff;border:none;border-radius:8px;font-size:1rem;font-weight:600;cursor:pointer;transition:background .2s;margin-top:8px}button:hover:not(:disabled){background:var(--primary-hover)}button:disabled{opacity:.5;cursor:not-allowed}button.secondary{background:transparent;color:var(--primary);border:2px solid var(--primary)}button.secondary:hover:not(:disabled){background:#4f46e50d}button.danger{color:var(--error);border-color:var(--error)}.button-group{display:flex;gap:12px;flex-wrap:wrap;margin-top:16px}.link-btn{background:transparent;color:var(--text-light);font-size:.9rem;font-weight:400;padding:8px;margin-top:0}.link-btn:hover{color:var(--primary);background:transparent}.ai-content{background:#f1f5f9;border-radius:8px;padding:20px;margin-bottom:16px;line-height:1.8;overflow-x:auto}.ai-content h1,.ai-content h2,.ai-content h3{margin-top:16px;margin-bottom:8px}.ai-content p{margin-bottom:12px}.ai-content ul,.ai-content ol{padding-left:24px;margin-bottom:12px}.ai-content code{background:#e2e8f0;padding:2px 6px;border-radius:4px;font-size:.9em}.hint{color:var(--text-light);font-style:italic;margin:12px 0}.upload-area{margin:16px 0}.upload-area input[type=file]{display:none}.preview{margin:16px 0;text-align:center}.preview img{max-width:100%;max-height:400px;border-radius:8px;border:2px solid var(--border)}.mistake-tags{margin:16px 0}.tags{display:flex;flex-wrap:wrap;gap:8px;margin-top:8px}.tag{background:#eff6ff;color:#3b82f6;padding:4px 12px;border-radius:20px;font-size:.85rem;border:1px solid #bfdbfe}.mistake-table{width:100%;border-collapse:collapse;margin:16px 0}.mistake-table th,.mistake-table td{padding:10px 12px;text-align:left;border-bottom:1px solid var(--border)}.mistake-table th{font-weight:600;color:var(--text-light);font-size:.85rem;text-transform:uppercase}.count-badge{background:#eff6ff;color:#3b82f6;padding:2px 8px;border-radius:12px;font-weight:600;font-size:.85rem}.loading{text-align:center;padding:48px 24px}.spinner{width:40px;height:40px;border:4px solid var(--border);border-top-color:var(--primary);border-radius:50%;animation:spin .8s linear infinite;margin:0 auto 16px}@keyframes spin{to{transform:rotate(360deg)}}.error{background:#fef2f2;border:1px solid #fecaca;color:var(--error);padding:16px;border-radius:8px;margin-bottom:16px}footer{display:flex;justify-content:center;gap:8px;padding:16px 0;border-top:1px solid var(--border);margin-top:24px}.header-row{display:flex;justify-content:space-between;align-items:center}.logout-btn{font-size:.8rem;color:var(--text-light)}.login-container{display:flex;justify-content:center;align-items:center;min-height:80vh}.login-title{color:var(--primary);font-size:1.5rem;margin-bottom:20px;text-align:center}.login-error{color:var(--error);font-size:.9rem;margin:0}input[type=password]{padding:12px;border:2px solid var(--border);border-radius:8px;font-size:1rem;transition:border-color .2s}input[type=password]:focus{outline:none;border-color:var(--primary)}.session-list-title{margin-top:24px;margin-bottom:12px;font-size:1rem;color:var(--text-light)}.session-list{display:flex;flex-direction:column;gap:8px}.session-item{display:flex;justify-content:space-between;align-items:center;padding:12px 16px;background:var(--bg);border-radius:8px;cursor:pointer;transition:background .2s;border:1px solid var(--border)}.session-item:hover{background:#e8ecf4}.session-info{display:flex;flex-direction:column;gap:2px}.session-meta{font-size:.8rem;color:var(--text-light)}.session-topic{font-size:.8rem;color:var(--text);font-weight:400}.session-step{font-size:.8rem;color:var(--primary)}.session-delete{background:transparent;color:var(--text-light);font-size:1.3rem;padding:4px 8px;margin:0;border:none;line-height:1}.session-delete:hover{color:var(--error);background:transparent}.progress-bar{display:flex;justify-content:space-between;align-items:center;margin-bottom:24px;padding:0 8px}.progress-step{display:flex;flex-direction:column;align-items:center;gap:4px;flex:1}.progress-dot{width:12px;height:12px;border-radius:50%;background:var(--border);transition:all .2s}.progress-step.active .progress-dot{background:var(--primary)}.progress-step.current .progress-dot{background:var(--primary);box-shadow:0 0 0 3px #4f46e54d}.progress-label{font-size:.7rem;color:var(--text-light)}.progress-step.active .progress-label{color:var(--primary);font-weight:600}.nav-buttons{display:flex;justify-content:space-between;align-items:center;padding:12px 0;margin-top:16px}.header-actions{display:flex;gap:4px;align-items:center}.ask-overlay{position:fixed;inset:0;background:#00000080;display:flex;justify-content:center;align-items:flex-start;padding:48px 16px;z-index:100;overflow-y:auto}.main-layout{flex:1}.main-layout-with-ask{display:flex;gap:16px;align-items:flex-start}.main-layout-with-ask .main-content{flex:1;min-width:0}.ask-side-panel{flex:0 0 380px;position:sticky;top:16px;max-height:calc(100vh - 120px);overflow-y:auto}.ask-card{width:100%}@media(max-width:860px){.main-layout-with-ask{flex-direction:column}.ask-side-panel{flex:none;width:100%;position:static;max-height:none}}.ask-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:12px}.ask-header h2{margin-bottom:0}.provider-options{display:flex;gap:12px;margin-top:8px}.provider-btn{flex:1;display:flex;flex-direction:column;align-items:center;gap:4px;padding:16px;background:var(--bg);color:var(--text);border:2px solid var(--border);border-radius:8px;cursor:pointer;transition:all .2s}.provider-btn:hover{border-color:var(--primary);background:var(--bg)}.provider-btn.active{border-color:var(--primary);background:#4f46e514}.provider-btn strong{font-size:1rem}.provider-btn span{font-size:.8rem;color:var(--text-light)}.ka-start-btn{background:linear-gradient(135deg,#f59e0b,#d97706);margin-top:8px}.ka-start-btn:hover{background:linear-gradient(135deg,#d97706,#b45309)}.ka-subtitle{color:var(--text-light);margin-bottom:16px}.ka-total-progress{margin-bottom:20px}.ka-progress-label{font-size:.85rem;color:var(--text-light);margin-bottom:6px}.ka-progress-bar{width:100%;height:10px;background:var(--border);border-radius:5px;overflow:hidden}.ka-progress-bar-small{height:6px;margin-top:6px}.ka-progress-fill{height:100%;background:linear-gradient(90deg,var(--success),#16a34a);border-radius:5px;transition:width .3s ease}.ka-topic-list{display:flex;flex-direction:column;gap:8px}.ka-topic-card{display:flex;align-items:center;gap:12px;padding:14px 16px;background:var(--bg);border:1px solid var(--border);border-radius:8px;cursor:pointer;transition:all .2s}.ka-topic-card:hover{background:#e8ecf4;border-color:var(--primary)}.ka-topic-complete{border-color:var(--success);background:#f0fdf4}.ka-topic-number{width:32px;height:32px;background:var(--primary);color:#fff;border-radius:50%;display:flex;align-items:center;justify-content:center;font-weight:700;font-size:.9rem;flex-shrink:0}.ka-topic-complete .ka-topic-number{background:var(--success)}.ka-topic-info{flex:1;min-width:0}.ka-topic-info strong{display:block;font-size:.95rem}.ka-topic-desc{font-size:.8rem;color:var(--text-light)}.ka-topic-stats{font-size:.75rem;color:var(--text-light);margin-top:2px;display:block}.ka-badge-done{color:var(--success);font-size:1.3rem;font-weight:700;flex-shrink:0}.back-link{background:transparent;color:var(--text-light);font-size:.9rem;padding:4px 0;margin-bottom:8px;text-align:left}.back-link:hover{color:var(--primary);background:transparent}.ka-tabs{display:flex;gap:0;margin-bottom:16px;border-bottom:2px solid var(--border)}.ka-tab{flex:1;background:transparent;color:var(--text-light);border:none;border-bottom:2px solid transparent;margin-bottom:-2px;padding:10px 16px;font-size:.9rem;font-weight:600;cursor:pointer;border-radius:0;transition:all .2s}.ka-tab:hover{color:var(--primary);background:transparent}.ka-tab-active{color:var(--primary);border-bottom-color:var(--primary)}.ka-exercise-image{margin-bottom:12px;text-align:center}.ka-exercise-image img{max-width:100%;height:auto}.ka-ai-empty{text-align:center;padding:32px 16px}.ka-ai-empty p{margin-bottom:16px;color:var(--text-light)}.ka-ai-section .loading{padding:32px 0}.ka-exercise-dots{display:flex;gap:6px;flex-wrap:wrap;margin-bottom:12px}.ka-dot{width:32px;height:32px;border-radius:50%;padding:0;margin:0;font-size:.8rem;font-weight:600;background:var(--border);color:var(--text-light);border:2px solid transparent;display:flex;align-items:center;justify-content:center}.ka-dot-active{background:var(--primary);color:#fff}.ka-dot-done{background:var(--success);color:#fff}.ka-dot-active.ka-dot-done{background:var(--success);border-color:var(--primary)}.ka-exercise-counter{font-size:.85rem;color:var(--text-light);margin-bottom:16px;display:flex;align-items:center;gap:8px}.ka-done-badge{background:#dcfce7;color:#16a34a;padding:2px 8px;border-radius:12px;font-size:.75rem;font-weight:600}.ka-exercise-text{background:#f8fafc;border-left:4px solid var(--primary);border-radius:4px;padding:16px;margin-bottom:16px;line-height:1.8}.ka-exercise-text p{margin-bottom:8px}.ka-exercise-text p:last-child{margin-bottom:0}.ka-actions{display:flex;gap:8px;flex-wrap:wrap}.ka-photo-section,.ka-feedback{margin-bottom:16px}.ka-solution{background:#f0fdf4;border:1px solid #bbf7d0;border-radius:8px;padding:16px;margin-bottom:16px;line-height:1.8}.ka-solution h3{color:#16a34a;margin-bottom:8px}.ka-solution p{margin-bottom:8px}.ka-nav{display:flex;justify-content:space-between;margin-top:16px;padding-top:16px;border-top:1px solid var(--border)}.ka-complete-banner{background:linear-gradient(135deg,#dcfce7,#bbf7d0);color:#15803d;padding:16px;border-radius:8px;text-align:center;font-weight:600;margin-top:16px}.ka-reset-btn{background:transparent;font-size:.85rem;margin-top:12px;padding:6px 12px}button.danger{background:transparent}button.danger:hover{background:#ef444414}.ka-exercise-text .katex-display,.ka-solution .katex-display,.ai-content .katex-display{margin:12px 0;overflow-x:auto}.ka-exercise-text .katex,.ka-solution .katex{font-size:1.1em}.past-topics{margin-top:-4px;margin-bottom:8px}.past-topics-label{font-size:.8rem;color:var(--text-light)}.past-topics-chips{display:flex;flex-wrap:wrap;gap:6px;margin-top:6px}.past-topic-chip{background:#4f46e514;color:var(--primary);border:1px solid rgba(79,70,229,.2);padding:4px 12px;border-radius:20px;font-size:.82rem;cursor:pointer;transition:all .2s}.past-topic-chip:hover{background:var(--primary);color:#fff}@media(max-width:480px){.app{padding:12px}.step-card{padding:16px}.button-group{flex-direction:column}}